Ethylenediaminetetraacetic acid or its ammonium salt semiconductor process residue removal process

ABSTRACT

An ethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammonium salt thereof residue cleaning composition removes photoresist and other residue from integrated circuit substrates. The balance of the composition is desirably made up of water, preferably high purity deionized water, or another suitable polar solvent. A process for removing photoresist or other residue from a substrate, such as an integrated circuit semiconductor wafer including titanium metallurgy, comprises contacting the substrate with the composition for a time and at a temperature sufficient to remove the photoresist or other residue from the substrate. Use of the ethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammonium salt thereof in the composition and process provides superior residue removal without attacking titanium or other metallurgy, oxide or nitride layers on the substrate.

ORIGIN OF THE INVENTION

This application is a division of application Ser. No. 08/833,382pending, filed Apr. 14, 1997, which is a continuation-in-part ofapplication Ser. No. 08/628,060, filed Apr. 17, 1996, now U.S. Pat. No.6,187,750 which is in turn a continuation-in-part of application Ser.No. 08/078,657, filed Jun. 21, 1993, now abandoned, which is in turn acontinuation-in-part of application Ser. No. 07/911,102, filed Jul. 9,1992, now U.S. Pat. No. 5,334,332, which was a continuation-in-part ofapplication Ser. No. 07/610,044, filed Nov. 5, 1990, now U.S. Pat. No.5,279,771. The disclosures of those applications are hereby incorporatedby reference in this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a cleaning composition andprocess for removal of organic, organometallic and metal oxide residuesfrom substrates. More particularly, it relates to such a composition andprocess for removing semiconductor device fabrication residues fromsemiconductor device substrates, such as etching residues after plasmaetching processes in the fabrication of integrated circuits on siliconwafers and similar processes. Most especially, it relates to such acomposition and process which is effective for the removal of thesematerials while avoiding substantial attack on metal or insulationlayers employed in integrated circuits, including titanium layers.

2. Description of the Prior Art

As integrated circuit manufacturing has become more complex and thedimensions of circuit elements fabricated on silicon or othersemiconductor wafers have become smaller, continued improvement intechniques used to remove residues formed from such materials has beenrequired. Oxygen plasma oxidation is often used for removal ofphotoresist or other polymeric materials after their use during thefabrication process has been completed. Such high energy processestypically result in the formation of organometallic and other residueson sidewalls of the structures being formed in the fabrication process.

A variety of metal and other layers are commonly employed in integratedcircuit fabrication, including aluminum, aluminum/silicon/copper,titanium, titanium nitride, titanium/tungsten, tungsten, silicon oxide,polysilicon crystal, and the like. The use of such different layersresults in the formation of different organometallic residues in thehigh energy processes. In addition to being effective for removing suchresidues, cleaning compositions should also not attack the differentmetallurgies or insulators used in integrated circuit fabrication.

A variety of residue removal compositions and processes suitable forintegrated circuit fabrication have been developed and marketed by EKCTechnology, Inc., the assignee of the present application. Some of thesecompositions and processes are also useful for stripping photoresist,polyamide or other polymeric layers from substrates in integratedcircuit fabrication, and EKC has also developed a variety ofcompositions and processes for stripping such polymeric layers fromsubstrates in integrated circuit fabrication. Such compositions andprocesses are disclosed in the following commonly assigned issuedpatents: U.S. Pat. No. 5,482,566, issued Jan. 9, 1996 to Lee; U.S. Pat.No. 5,399,464, issued Mar. 21, 1995 to Lee; U.S. Pat. No. 5,381,807,issued Jan. 17, 1995 to Lee; U.S. Pat. No. 5,334,332, issued Aug. 2,1994 to Lee; U.S. Pat. No. 5,279,771, issued Jan. 18, 1994 to Lee; U.S.Pat. No. 4,824,763, issued Apr. 25, 1989 to Lee and U.S. Pat. No.4,395,348, issued Jul. 26, 1983 to Lee. These compositions have achievedsubstantial success in integrated circuit fabrication applications.However, further development of integrated circuits and theirfabrication processes have created a need for improvement in residueremoval compositions and processes.

As a result of a continuous effort to decrease critical dimension sizein the integrated circuit industry, such as in the fabrication ofsub-micron size devices, etching residue removal and substratecompatibility with chemicals employed in wet processing is becoming moreand more critical for obtaining acceptable yield in very large scaleintegration (VLSI) and ultra large scale integration (ULSI) processes.The composition of such etching residue is generally made up of theetched substrates, underlying substrate, photoresist and etching gases.The substrate compatibility of the wafers with wet chemicals is highlydependent on the processing of the polysilicon, multilevelinterconnection dielectric layers and metallization in thin filmdeposition, etching and post-etch treatment of the wafers, which areoften quite different from one fabrication process to another. Some ofthe above compositions have produced corrosion on certain metal orinsulator substrates, such as those including a titanium metal layer.Titanium has become more widely used in semiconductor manufacturingprocesses. It is employed both as a barrier layer to preventelectromigration of certain atoms and as an antireflective layer on topof other metals.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide an improvedcomposition for residue removal and process using such a compositionsuitable for meeting current semiconductor fabrication requirements.

It is another object of the invention to provide such a composition andprocess which is suitable for removing residues from wafers and othersubstrates including one or more titanium metal layers withoutsubstantial attack on such titanium layers.

The attainment of these and related objects may be achieved through useof the residue removal composition and process herein disclosed. Aresidue removal composition in accordance with this invention comprisesethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammoniumsalt thereof and water or a polar organic solvent. A process forremoving a residue from a substrate in accordance with this inventioncomprises contacting the substrate with a composition that containsethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammoniumsalt thereof for a time and at a temperature sufficient to remove theresidue from the substrate. When the ethylenediaminetetraacetic acid isused in its acid form, it can either be employed alone as the principalactive ingredient or in combination with ammonia to form ammonium saltin situ.

In practice, we have found that use of an ethylenediaminetetraaceticacid or a mono-, di-, tri- or tetraammonium salt thereof gives a residueremoving composition that attacks titanium, for example, at least about3 times less than prior compositions. At the same time, theethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammoniumsalt thereof containing composition gives at least equivalentperformance as a residue removing composition to prior art cleaningcompositions.

The attainment of the foregoing and related objects, advantages andfeatures of the invention should be more readily apparent to thoseskilled in the art, after review of the following more detaileddescription of the invention, taken together with the drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-9C are scanning electron microscope (SEM) photographs showingcomparative results achieved using the composition and process of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The ethylenediaminetetraacetic acid (EDTA) or a mono-, di-, tri- ortetraammonium salt thereof suitable for use in the invention preferablyhave relatively high decomposition temperatures. Preferred higherdecomposition temperature specific examples of such EDTA salts includediammonium EDTA and tetraammonium EDTA.

The composition desirably contains at least about 1 to 50% by weight ofat least one ethylenediaminetetraacetic acid or a mono-, di-, tri- ortetraammonium salt thereof; optionally, from about 25% to about 75% byweight of one or more amines or alkanolamines; optionally, from about25% to about 75% percent by weight of an organic polar solvent;optionally, from about 0.15% to about 10% by weight of an organic orinorganic ammonium salt; optionally, from about 5% to about 25% byweight of an additional chelating agent, such as catechol or gallicacid; and from about 25% to about 75% by weight of water (e.g., as partof the EDTA or its ammonium salt). When ethylenediaminetetraacetic acidis employed in the acid form, the composition may optionally containfrom about 1% to about 10% percent by weight of ammonia.

Ethylenediaminetetraacetic acid (EDTA) is one of the most widely usedchelating agents in the world. Its ammonium salts, soluble in water andmost of the organic solvents, should be stronger chelants than EDTA dueto extra ammonium chelating sites. These organic ammonium salts are goodstarting chemicals for ammonium based integrated circuit cleaningformulations.

Suitable amines for the composition include ethylene diamine, diethylenetriamine, 2-methyleneaminopropylenediamine, and the like.

Examples of suitable alkanolamines for the composition includemonoethanolamine, diethanolamine, triethanolamine,tertiarybutyldiethanolamine, isopropanolamine, diisopropanolamine(2-amino-1-propanol, 1-amino-2-propanol), triisopropanolamine,3-amino-1-propanol, isobutanolamine, 2-(2-aminoethoxy)ethanol(diglycolamine), 2-amino-2-ethoxy-propanol, methylethanol amine,N,N-diethyl hydroxylamine, and the like.

Suitable examples of polar solvents for the composition, in addition towater, include dimethyl sulfoxide, ethylene glycol, ethylene glycolalkyl ether, diethylene glycol alkyl ether, triethylene glycol alkylether, propylene glycol, propylene glycol alkyl ether, N-substitutedpyrrolidone, sulfolane, dimethyl acetamide, and the like. Additionalpolar solvents as known in the art can also be used in the compositionof the present invention.

Suitable examples of ammonium salts for the composition include organicammonium salts in addition to EDTA ammonium salts, such as ammoniumtartrate, ammonium citrate, ammonium formate; ammonium glucomate;inorganic ammonium salts, such as ammonium fluoride, ammonium nitrate,ammonium thiosulfate, ammonium persulfate, ammonium bicarbonate,ammonium phosphate, and the like.

The residue cleaning compositions of the present composition areeffective in removing organometallic and metal oxide residue from avariety of integrated circuit silicon wafer substrates, including metallayers, such as aluminum or titanium, oxide layers, such as siliconoxides, nitride layers, such as silicon nitride, and the like. Thecleaning compositions of the present invention are also effective inremoving organometallic and metal oxide residue generated on thesubstrate of etching equipment utilized in the fabrication of integratedcircuits. Examples of commercially available etching equipment includethat available from Lam Research, Tegal, Electrotech, Applied Materials,Tokyo Electron, Hitachi and the like.

The method of cleaning a substrate using the cleaning compositions ofthe present invention involves contacting a substrate havingorganometallic and metal oxide residue thereon with a stripping andcleaning composition of the present invention for a time and at atemperature sufficient to remove the residue. The substrate is generallyimmersed in the stripping and cleaning composition. The time andtemperature are determined based on the particular material beingremoved from a substrate. Generally, the temperature is in the range offrom about ambient or room temperature to about 120° C. and the contacttime is from about 2 to 60 minutes.

The substrate may then be rinsed in a polar solvent, such as isopropylalcohol, followed by a deionized water rinse. The substrate is thenmechanically dried, such as with a spin drier, or nitrogen blow dried.

The following represent non-limiting examples and describe the inventionfurther.

Examples of cleaning compositions according to the present inventionsuitable for removing resist or other organic residues from a substrateare set forth in Table I below.

TABLE 1 Other Alkanol/ Cleaning EDTA or Component Amine SolventComposition Salt Wt. % Wt. % Wt. % Wt % A 17.5% TAE 5% Catechol 60% DGA17.5% Water B 5% DAE 5% Citric Acid 12.5% HDA; 72.5% Water 5% MEA C 5%DAE 17.5% HDA; 17.5% Water 60% DGA; D 5% EDTA 15% HDA; 15% Water, 10%DHA 55% DMSO E 5% DAE 15% HDA; 15% Water, 10% DHA 55% DMSO F 5% DAE 20%HDA; 20% Water, 55% DMSO G 5% TAE 20% HDA; 20% Water; 55% DMAC H 13%EDTA 5% Catechol 60% DGA 19% Water 3% NH3 (28-30% Aq. Sol'n)Abbreviations: EDTA = ethylenediaminetetraacetic acid DAE = diammoniumEDTA TAE = tetraammonium EDTA DGA = diglycolamine HDA = hydroxylamineMEA = monoethanolamine DMSO = dimethylsulfoxide DMAC = dimethylacetamideDHA = N,N-diethyl-hydroxylamine

The following experimental procedure was used with the abovecompositions. The chemicals were used as received. The solutions wereprepared by stirring the mixture at room temperature until a clearsolution was obtained. Heating was required in some cases to acceleratethe solvation of solid components.

Ashed-via, unashed wafers and metal wafers with a TiN/Al—Cu/Ti/TiN/Ti orTiN/Al—Cu—Si/Ti stack were processed in these prepared cleaningsolutions for 30 minutes at 45° C., 55° C. and 65° C., depending on thenature of the formulations. The wafers were broken into pieces beforeand after processing in these different cleaning solutions andsubsequently viewed under a FE Hitachi 4500 Scanning Electron Microscopefor post ash residue removal in vias and substrate compatibility onmetal stacks.

EXAMPLE 1

A via opening with a size of 1.2 micron in a silicon oxide dielectriclayer was etched through a photoresist patterned opening using astandard silicon oxide plasma etching process. The photoresist wasremoved by oxygen plasma ashing. FIG. 1A is a micrograph of a scanningelectron microscope (SEM) image for a representative substrate of thetype used in this example, showing that heavy organometallic etchresidue remained on the substrate surface, particularly around the viaopening. The substrate was then processed in composition A for 30minutes at 55° C. FIG. 1B, the resulting SEM photograph, shows thatcomposition A removed all the organometallic residue.

EXAMPLE 2

This example shows that composition A does not attack a titaniummetallurgy. A sandwich metal thin film substrate of TiN/Al—Cu/Ti/TiN/Timetallurgy was patterned and etched in a plasma metal etcher. FIG. 2Ashows that there is organometallic residue left on the metal linesurface after photoresist removal by oxygen plasma ashing. The wafer wasexposed to composition A at 55° C. for 30 minutes, with substantiallycomplete removal of the organometallic residue and no attack on thetitanium metallurgy, as shown in FIG. 2B.

EXAMPLE 3

The procedures of Examples 1 and 2 were repeated with composition B butat a cleaning temperature of 45° C. FIGS. 3A and 3B show the resultsobtained. Approximately a 90% cleaning of the ashed via wafer wasobtained, as determined by visual observation of FIG. 3A. There waseither no metal corrosion or perhaps just the start of attack on theunderlying aluminum metallurgy. FIG. 3B shows complete cleaning of aTiN/Al—Cu/Ti/TiN/Ti stack wafer, with no metal corrosion, or juststarting to attack the aluminum layer in the stack metallurgy.

EXAMPLE 4

The procedures of Example 3 were repeated with composition C, also at acleaning temperature of 45° C. FIGS. 4A and 4B show the resultsobtained. Complete cleaning of the ashed via wafer was obtained, asdetermined by visual observation of FIG. 4A. There was complete controlof metal corrosion. FIG. 4B shows complete cleaning of theTiN/Al—Cu/Ti/TiN/Ti stack wafer, as shown by the clean appearance of thetop TiN layer with no metal corrosion.

EXAMPLE 5

The procedures of Example 3 were repeated with composition D but at acleaning temperature of 65° C. FIGS. 5A, 5B and 5C show the resultsobtained. A 90% cleaning of the ashed via wafer was obtained, asdetermined by visual observation of FIG. 5A. There was no metalcorrosion. FIG. 5B shows almost complete cleaning of residue an unashedvia wafer, with some residue only on the bottom of the via. FIG. 5Cshows complete cleaning of the TiN/Al—Cu/Ti/TiN/Ti stack wafer, with nometal corrosion.

EXAMPLE 6

The procedures of Example 5 were repeated with composition E. FIGS. 6A,6B and 6C show the results obtained. Surface and sidewall cleaning ofthe ashed via wafer, with residue only on the bottom of the via wasobtained, as determined by visual observation of FIG. 6A. There was nometal corrosion. FIG. 6B shows complete cleaning of residue on thesurface and sidewall of the via of the no-ash wafer, with some residueonly on the bottom of the via, with no metal corrosion. FIG. 6C showscomplete cleaning of the TiN/Al—Cu—Si/Ti stack wafer.

EXAMPLE 7

The procedures of Example 5 were repeated with composition F. FIGS. 7A,7B and 7C show the results obtained. The sidewall and bottom of the viaof the ashed via wafer were not quite cleaned, as determined by visualobservation of FIG. 7A. There was no metal corrosion. FIG. 7B showscomplete cleaning of residue on the no-ash wafer, with only a possiblesmall aluminum undercut. FIG. 7C shows complete cleaning of theTiN/Al—Cu/Ti/TiN/Ti stack wafer, with no metal corrosion.

EXAMPLE 8

The procedures of Example 5 were repeated with composition G. FIGS. 8A,8B and 8C show the results obtained. Surface and sidewall cleaning ofthe ashed via wafer, with residue only on the bottom of the via, wasobtained, as determined by visual observation of FIG. 8A. There was nometal corrosion. FIG. 8B shows complete cleaning of residue on thesurface and sidewall of the via of the no-ash wafer, with residue onlyon the bottom of the via, with no metal corrosion. FIG. 8C showscomplete cleaning of the TiN/Ai—Cu/Ti/TiN/Ti stack wafer, with either nometal corrosion or just a start of titanium corrosion.

EXAMPLE 9

The procedure of Example 1 was repeated with composition H on threedifferent wafer types. When composition H was mixed, a substantialamount of heat was generated, indicating the in situ formation oftetraammonium EDTA according to the equation:

EDTA+4NH3.H2O→(NH₃)₄EDTA+4H₂O.

FIGS. 9A, 9B and 9C show the results obtained. The ashed via wafer wasonly about 80% cleaned, as determined by visual observation of FIG. 9A.Some bulk polymer strips were observed. The TiN/Al—Cu/Ti/TiN/Ti stackwafer was completely cleaned and showed no corrosion of either thealuminum or the titanium layers, as shown in FIG. 9B. TheTi/Al—Cu—Si/TiN stack was also completely cleaned with no aluminum or Ticorrosion, as shown in FIG. 9C.

It should now be readily apparent to those skilled in the art that anovel composition and process capable of achieving the stated objects ofthe invention has been provided. The improved ethylenediaminetetraaceticacid or a mono-, di-, tri- or tetraammonium salt thereof basedcomposition and process using such a composition of this invention issuitable for meeting current semiconductor fabrication requirements. Thecomposition and process is suitable for removing photoresist residuesand other residues from wafers and other substrates including one ormore titanium metal layers without substantial attack on such titaniumlayers.

It should further be apparent to those skilled in the art that variouschanges in form and details of the invention as shown and described maybe made. It is intended that such changes be included within the spiritand scope of the claims appended hereto.

What is claimed is:
 1. A process for removing photoresist from asubstrate which comprises contacting the substrate with a compositioncomprising from about 17.5% to about 50% by weight of at least oneethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammoniumsalt thereof; from about 25% to about 75% by weight of a polar organicsolvent; from about 0.15% to about 10% by weight of an ammonium saltselected from the group consisting of ammonium tartrate, ammoniumcitrate, ammonium formate, ammonium glucomate, ammonium fluoride,ammonium nitrate, ammonium thiosulfate, ammonium persulfate, ammoniumbicarbonate, and ammonium phosphate and water, for a time and at atemperature sufficient to remove the photoresist or other polymericmaterial from the substrate.
 2. The process of claim 1 wherein the timeis from about 2 to about 60 minutes and the temperature is from roomtemperature to about 120 C.
 3. The process of claim 1 wherein thecomposition further comprises at least one amine or alkanolamine.
 4. Theprocess of claim 1 wherein the ammonium salt ofethylenediaminetetraacetic acid is formed in the composition fromethylenediaminetetraacetic acid and ammonia.
 5. The process of claim 1wherein the composition further comprises an additional chelating agent.6. The process of claim 5 wherein the additional chelating agent iscatechol or gallic acid.
 7. The process of claim 1 wherein the substratecomprises titanium.
 8. The process of claim 1 wherein the substratecomprises a titanium layer of an integrated circuit.
 9. The process ofclaim 3 wherein the at least one amine or alkanolamine is present in thecomposition in an amount of from about 25% to about 75% by weight. 10.The process of claim 3 wherein the at least one amine or alkanolamine isselected from the group consisting of ethylene diamine, diethylenetriamine, 2-methyleneaminopropylenediamine, monoethanolamine,diethanolamine, triethanolamine, tertiarybutyldiethanolamine,isopropanolamine, diisopropanolamine, triisopropanolamine,3-amino-1-propanol, isobutanolamine, 2-(2-aminoethoxy)ethanol,2-amino-2-ethocy-propanol, methylethanol amine, and N,N-diethylenehydroxylamine.
 11. The process of claim 6 wherein the additionalchelating agent is present in the composition in an amount of from about5% to about 25% by weight.
 12. The process of claim 1 wherein the wateris present in the composition in an amount of from about 25% to about75% by weight.
 13. The process of claim 1 wherein the organic polarsolvent is selected from the group consisting of dimethyl sulfoxide,ethylene glycol, ethylene glycol alkyl ether, diethylene glycol alkylether, triethylene glycol alkyl ether, propylene glycol, propyleneglycol alkyl ether, N-substituted pyrrolidone, sulfolane, and dimethylacetamide.
 14. A method for removing photoresist from a substrate whichcomprises contacting the substrate with a composition comprising fromabout 13% to about 50% by weight of at least oneethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammoniumsalt thereof; from about 25% to about 75% by weight of a polar organicsolvent; from about 0.15% to about 10% by weight of an ammonium saltselected from the group consisting of ammonium tartrate, ammoniumcitrate, ammonium formate, ammonium glucomate, ammonium fluoride,ammonium nitrate, ammonium thiosulfate, ammonium persulfate, ammoniumbicarbonate, and ammonium phosphate; and from about 5% to about 75% byweight water, for a time and at a temperature sufficient to remove thephotoresist or other polymeric material from the substrate.
 15. Themethod of claim 14 wherein the composition further comprises from about25% to about 75% by weight of at least one amine or alkanolamine. 16.The method of claim 14 wherein the composition contains from about 17.5%to about 50% by weight of di-, tri-, or tetraammonium salt ofethylenediaminetetraacetic acid.
 17. The method of claim 14 wherein thetime is from about 2 to about 60 minutes and the temperature is fromroom temperature to about 120° C.
 18. The method of claim 14 wherein thesubstrate comprises titanium.
 19. The method of claim 14 wherein thesubstrate comprises a titanium layer of an integrated circuit.
 20. Themethod of claim 15 wherein the at least one amine or alkanolamine isselected from the group consisting of ethylene diamine, diethylenetriamine, 2-methyleneaminopropylenediamine, monoethanolamine,diethanolamine, triethanolamine, tertiarybutyldiethanolamine,isopropanolamine, diisopropanolamine, triisopropanolanine,3-amino-1-propanol, isobutanolamine, 2-(2-aminoethoxy)ethanol,2-amino-2-ethoxy-propanol, methylethanol amine, and N,N-diethylenehydroxylamine.
 21. The method of claim 14 wherein the organic polarsolvent is selected from the group consisting of dimethyl sulfoxide,ethylene glycol, ethylene glycol alkyl ether, diethylene glycol alkylether, triethylene glycol alkyl ether, propylene glycol, propyleneglycol alkyl ether, N-substituted pyrrolidone, sulfolane, and dimethylacetamide.